JP4977694B2 - Multi-layer protective film co-extruded with a film layer comprising at least one ethylene-vinyl alcohol-copolymer (EVOH), method for producing the same and method for using the same - Google Patents

Abstract

Barrier film for use in packaging, particularly for the packaging of foods and tobacco, in the form of a multi-layer film based on a biaxially oriented polyolefin film having at least one coextruded functional layer or barrier based on ethylene-vinyl alcohol copolymers (EVOH), which is produced by simultaneous drawing of a coextruded multi-layer primary film at temperatures of 145° C. and below, the ethylene content of the EVOH being below 40 mol % and the thickness of the EVOH layer being less than 5 μm, in particular less than 2 μm, thereby producing values for the oxygen permeability at 23° C. and 75% relative humidity (OTR; ASTM 3985) of better than 10 cm3/m2dbar, preferably better than 5 cm3/m2dbar.

Description

  The present invention uses crystalline polyolefin as a polymer constituting the film, and further has a coextruded layer composed of at least one ethylene-vinyl alcohol copolymer (EVOH) as a functional layer or a protective layer. The invention relates to a protective film for packaging, particularly for packaging foodstuffs, luxury goods and other sensitive products, in the form of a multilayer film with sufficient mechanical properties selected by a biaxially oriented film.

  The present invention further relates to a method for producing said film, packaging, and in particular a method for using a film for packaging foodstuffs and taste products utilizing the optical properties, strength properties, protective properties and optionally shrinkage properties of outstanding films.

  Packaging based on plastic film is now considered essential for modern food products. Depending on the product to be packaged, various demands arise on the plastic film. At that time, in the plastic film for packaging of foodstuffs and luxury goods, attention is paid to the characteristic that guarantees the stability of the packaged foodstuffs or luxury goods for the end-users until the sales channel and the consumption of the foodstuffs. .

Due to the high demands on packaging films, the current food and luxury goods sector has good strength, good optical properties and glossy metal films, especially made of aluminum or especially silicon oxide (SiO _x ) or aluminum oxide ( Polyester base films (PET, polyethylene terephthalate) with good coating properties for transparent ceramic coatings composed of AlO _x ) are often used. Thin metal or ceramic films are especially permeable to water vapor (water vapor transmission rate, WVTR, measured in g / (m ² d) or g / (m ² / 24h), ASTM-E96) and oxygen (oxygen transmission rate, OTR). , Measured at cm ³ / (m ² dbar), i.e. cm ³ / (m ² 24h) at 1 bar pressure, ASTM-3985) provides protective properties that can satisfy the high demands on the film. To ensure the film's weldability or sealability required for packaging preparation, from an additional outer polyolefin layer such as high density polyethylene (HDPE) or low density polyethylene (LDPE) with a metal or ceramic coating A polyethylene layer is usually provided. This polyester film satisfies high quality requirements, but in particular has a drawback that the polyester polymer is relatively expensive and has a relatively high density.

Therefore, instead of biaxial polyethylene terephthalate (BOPET) film laminated in an indirect manufacturing process (offline) with polyvinylidene chloride (PVDC) or silicon oxide (SiO _x ), it is co-extruded in a direct manufacturing process (inline) Attempts have been made to rely on other polyolefin films, especially polypropylene films. The film can be manufactured relatively cheaply (even as a protective film). However, to compete with the more expensive but higher quality biaxial polyethylene terephthalate (BOPET) film, the polyolefin film must also have no significant drawbacks in terms of optical properties, strength properties and protective properties.

  For example, combining a polyolefin layer based on a copolymer of polyethylene, polypropylene or other olefins with a layer made of an ethylene-vinyl alcohol copolymer (EVOH) known as good protective properties in a protective film Is known. In addition, since the protective properties deteriorate when air humidity enters, an ethylene-vinyl alcohol copolymer layer is usually placed on the core of the multilayer film, and the ethylene-vinyl alcohol copolymer layer is disposed on both sides of the polyolefin layer. It is also known to shield preferably from the surroundings.

  It is also important that the molar concentration of the vinyl alcohol group in the ethylene-vinyl alcohol copolymer is sufficiently high relative to the molar concentration of the ethylene group, and that the protective properties of the ethylene-vinyl alcohol copolymer layer are usually improved. is there. However, as the concentration of the polar vinyl alcohol group in the copolymer increases, the intolerance to nonpolar polymers such as polyolefins also increases.

  Furthermore, it is known that the mechanical properties and optical properties of the polyolefin film can be improved by biaxial stretching (providing biaxial orientation), and the protective properties of the ethylene-vinyl alcohol copolymer protective layer can also be improved by biaxial stretching. .

  However, similarly, the polyolefin layer, in particular, the polypropylene layer and the ethylene-vinyl alcohol copolymer layer are in direct contact with each other and do not adhere well and have non-affinity (non-adhesiveness). It is known that different layers crystallize in different ways to form the desired optical properties under different conditions. Thus, specially made of specially modified (modified) polyolefins that facilitate the simultaneous stretching of the polyolefin and the ethylene-vinyl alcohol copolymer layer or act as an adhesive layer that generally allows simultaneous stretching in certain cases in general. It is generally known to provide intermediate layers to improve the compatibility or affinity of the layers.

  Nevertheless, the optimal optical properties, strength properties, and good protective properties under various conditions are formed when biaxiality is imparted to the multilayer polyolefin film provided with an ethylene-vinyl alcohol copolymer protective layer. Therefore, the effect of acting oppositely must be adjusted. Important prior art poses this problem and pursues various strategies to produce multilayer polyolefin films with an ethylene-vinyl alcohol copolymer protective layer that exhibits the best possible compromise to the achievable desired properties.

In Patent Document 1, a multilayer initial film having an ethylene-vinyl alcohol copolymer core layer and two polyolefin-outer layers are first stretched in a longitudinal direction (machine direction MD) in a temperature range of about 130 ° C. to 140 ° C. In addition, a method of sequentially stretching in two directions by stretching in the transverse direction (transverse direction TD) under a changing temperature condition in a range of approximately 150 ° C. to 160 ° C. is disclosed. The area stretch ratio obtained is in the range of a relatively slight area increase of only 6 (2 × 3) to 28 (4 × 7). In general, an ethylene-vinyl alcohol copolymer having an ethylene concentration of 25 to 75 mol% is known, but an ethylene-vinyl alcohol copolymer having an ethylene mol concentration of at least 45 mol% is used, and sufficient for stretching. It indicates that the protective film should be biaxially stretched by imparting such flexibility to the ethylene-vinyl alcohol copolymer. A multilayer film having an oxygen transmission rate (OTR) in the range of 12-13 cm ³ / m ² d was obtained at 20 ° C. and 0% relative humidity.

  Similarly, Patent Document 2 similarly stretches the same film in the biaxial direction with a higher area increase of 35 to 70 times, stretches the film in the machine direction at a temperature of 140 to 150 ° C., and laterally stretches the temperature in the range of 160 to 170. A similar method of stretching in the range of ° C. is shown. Again, the ethylene concentration in the ethylene-vinyl alcohol copolymer is set to at least 45%, indicating that a sufficient effect is obtained during stretching.

  Patent Document 3 proposes a general form of stretching a polypropylene-based multilayer film having a protective layer of an ethylene-vinyl alcohol copolymer of a comparative example as simultaneous stretching at an area expansion ratio of 49 to 64 times. Actually, there is no description or explanation of the only embodiment, and in Patent Document 3, it is understood that the conditions for stretching used for the polymer quality for each layer are “simultaneous stretching”. Similarly, a more accurate description of film quality is lacking. Therefore, Patent Document 3 does not show specific practicable requirements for experts as a whole.

  Starting from the knowledge of the expert, in order to perform biaxial stretching on polypropylene with an area stretch ratio in the range 49-64, a predetermined stretching temperature should be maintained, and a known appropriate one corresponding to the description in Patent Document 3 Within the temperature range, a polypropylene-based multilayer film having an ethylene-vinyl alcohol copolymer core layer having an ethylene molar concentration of 40 mol% or less is stretched biaxially at the same time to give directionality, and stretching is generated. It is possible to observe tearing (configuration of network structure) of the ethylene-vinyl alcohol copolymer layer based on crystallization. When tearing occurs in the ethylene-vinyl alcohol copolymer layer, the protective properties are inevitably deteriorated and the film quality as a whole becomes insufficient. In this case, the stretching in Patent Document 3 using conventional stretching parameters results in a film in which the optical properties and the protective properties do not function.

  Patent Document 4 shows a predetermined modified polyolefin which is also suitable as an adhesive between the ethylene-vinyl alcohol copolymer layer and the polyolefin layer. A multi-layer test film comprising a polypropylene layer having a slight ethylene concentration, an adhesive layer according to the invention and an ethylene-vinyl alcohol copolymer layer having an ethylene concentration of 44 mol%, is a Sequentially stretched to 9 times increased area. There is no other description of adhesion regarding the other properties of the test film.

  Patent Document 5 and Patent Document 6 are two more recent patent applications that similarly show biaxial orientation of a multilayer polyolefin film having an ethylene-vinyl alcohol copolymer protective layer on the inside.

  Patent document 5 shows a thermoplastic multilayer biaxial direction shrink film. The intermediate layer is made of ethylene-vinyl alcohol-copolymer, and the outer layer is made of polyethylene-homopolymer or copolymer. The multilayer film that is simultaneously stretched preferably has a stretch ratio of 4 times or more both in the machine direction and in the transverse direction. An example in which the MD × TD stretch ratio is 4.5 × 4.5 or 5 × 5 corresponds to an area increase of 20.25 times or 25 times during stretching.

  If a polyethylene-homopolymer or copolymer in the outer layer is used, a heat-stable film cannot be produced and the disclosed process conditions cannot be directly transferred to the processing of polypropylene-based films. It also indicates that ethylene-vinyl alcohol copolymer qualities with an ethylene concentration in the range of approximately 28 to approximately 48 mol% can be used generally. However, as in the known prior art, only an ethylene-vinyl alcohol copolymer having an ethylene concentration of 44 mol% is used in all examples.

Patent document 6 shows the manufacturing method of the multilayer film which consists of a composite material of a polypropylene, an adhesive agent, and an ethylene-vinyl alcohol copolymer, and extends | stretches sequentially in a biaxial direction. The composite material is coextruded in the form of a layer of the same width in the form of a melt. Subsequently, the film is first stretched by a clip table in the longitudinal direction (MD) and then in the transverse direction (TD), and the temperature during stretching is in the range of 110-165 ° C, particularly 140-160 ° C in the machine direction. In the machine direction, it is 130 to 180 ° C, preferably 140 to 180 ° C. As the essence of the present invention, it is pointed out that all the five layers are gripped in common and simultaneously by the base clip during the transverse stretching. If only the ethylene-vinyl alcohol copolymer layer is gripped, the ethylene-vinyl alcohol copolymer layer is torn and the film becomes defective. An ethylene-vinyl alcohol copolymer having an ethylene concentration of 44 mol% is used to produce ethylene--of a film produced with the best oxygen protection with an oxygen barrier of about 5 cm ³ / m ² d at a temperature of 23 ° C. and humidity of 50% The final thickness of the vinyl alcohol copolymer layer is approximately 5 μm.

US Pat. No. 4,561,920 European Patent Application Publication No. 0,311,293 European Patent Application Publication No. 0688,667 European Patent Application Publication No. 0,758,675 International Publication No. WO2000 / 37253 International Publication No. WO2004 / 050353

  The object of the present invention is to take full advantage of the advantageous protective properties of ethylene-vinyl alcohol copolymers with low ethylene molar concentrations, in addition to the known advantageous properties of directional polypropylene films, in particular against oxygen and perfume. Providing a film having improved protection value and desired strength, at the same time transparent and glossy packaging film with outstanding impermeability to oxygen, water vapor, aroma and odor, and at least one ethylene- It is an object of the present invention to provide an improved protective film based on a biaxially oriented polyolefin layer provided with a vinyl alcohol copolymer protective layer, and a method for producing and using the same.

  This problem is solved by the film according to claims 1 to 18 having basic and preferred characteristics, the film production method according to claims 19 to 21 and the film use method according to claims 22 and 23 having the main characteristics.

  The present invention will be described in more detail below, while confirming and complementarily pointing out the expertise of those skilled in the art with reference to the prior art.

  A typical multilayer film comprises a support layer that determines at least one basic mechanical property of the main polymer that makes up the film, an outer protective layer or inner protective layer that achieves the desired protective properties, and printability. And an outer layer that provides the necessary sealing properties for the preparation or lamination of the coated or sealed package.

  Within the scope of the present invention, a seven-layer structure constituted by layer A / layer B / layer C / layer D / layer C / layer B / layer E is selected, and each layer A, layer B, layer C, layer D and Layer E is described in detail below individually.

  The central inner protective layer D is made of ethylene-vinyl alcohol-copolymer (EVOH). Adhesive layers C made of modified polyolefins, in particular modified polypropylene, are arranged on both sides adjacent to the inner protective layer D. A structural layer B consisting of a partially crystalline thermoplastic polyolefin or a mixture of partially crystalline thermoplastic polyolefins is placed adjacent to the adhesive layer C and is specially selected for the temperature conditions required for biaxial stretching. Or modified and preferably a polyolefin-based material as well. The outer layers A and E are likewise composed of partially crystalline thermoplastic polyolefins, in which the actual selection criterion is their surface properties after biaxial stretching.

  A multilayer melt is coextruded from a flat nozzle by a method known per se, and the resulting multilayer melt is brought into contact with a cooling roller to cure the bonding layer. Next, the film is stretched by a simultaneous stretching apparatus.

  A method suitable for carrying out the simultaneous stretching is a method in which the film is stretched to a flat film by a simultaneous stretching device equipped with a linear motor driving device (LISIM (registered trademark)). However, there is also a simultaneous film stretching method that is not very advantageous by mechanical simultaneous stretching device (MSO; mechanical simultaneous stretching device with chain drive) and tube film stretching method by bubble (BUBBLE) or double bubble (DOUBLE-BUBBLE) method. Similarly, it is included in the scope of the present invention.

  In the case of a biaxial polypropylene film with the usual properties for co-stretching, within the scope of the work leading to the present invention, a multilayered composite comprising ethylene-vinyl alcohol copolymers with an ethylene concentration of 44 mol% and 48 mol% can be used without problems. Although it could be stretched simultaneously, it was found that the oxygen permeability value of the film was insufficient. The actual draw ratio in this test was 8 to 1 in the machine direction and 5.5 to 1 in the transverse direction. The temperature was adjusted between 166 ° C. and 178 ° C. in the heating section, and the temperature was adjusted between 155 ° C. and 160 ° C. in the stretching section, and the same temperature conditions as those for producing a biaxial polypropylene film were the same. Final heat fixing was performed at 165 ° C.

  Multi-layered conjugates comprising ethylene-vinyl alcohol copolymers with ethylene concentrations of 44 mol% and 48 mol% are highly transparent and exhibit an invisible structure, but are too oxygen permeable for critical use.

  In contrast, a multi-layer bond using an ethylene-vinyl alcohol copolymer having an ethylene concentration of 27 to 38 mol% in a protective layer manufactured according to the above-described conventional conditions is completely ethylene-vinyl in a biaxial simultaneous stretching test. It had a strong network structure indicating destruction of the alcohol copolymer protective layer. Therefore, a high-quality protective film cannot be produced under conventional stretching conditions.

For high-quality protective layers, attempts have been made to obtain eigenvalues in the field of the following parameter ranges for the most important protective properties, mechanical properties and optical properties.
Oxygen permeability (OTR; ASTM-3985) at a temperature of 23 ° C. and a humidity of 75% should be 8 cm ³ / (m ² dbar) or less, and the thickness of the ethylene-vinyl alcohol copolymer protective layer is 10 μm. Should be less than. The total Young's coefficient of thermal expansion material (E module, ASTM-D-822) should exceed 2000 N / mm ² in the longitudinal and transverse directions and the tensile strength (ASTM-D-822) should be in the longitudinal and transverse directions in should exceed 300N / mm ^2. The gloss (ASTM-2457) should be above 80 and the turbidity (ASTM-1003) should be below 5%. In addition, a network structure should not be formed on the film.

The inventor has verified that a film having the above conditions can be surprisingly produced by selecting the material of layer B appropriately and carrying out simultaneous stretching at a temperature of 145 ° C. or lower. A multilayer film having an ethylene-vinyl alcohol copolymer protective layer having an ethylene concentration of 40 mol% or less with the required film properties, particularly an outstanding oxygen permeability value of 8 cm ³ / m ² dbar or less under the stretching conditions. Can be obtained. In order to prevent the tearing phenomenon (formation of a network structure) of the ethylene-vinyl alcohol copolymer layer, a simultaneous biaxial stretching speed of 50% / second or more, preferably 300% / second or more is applied.

  In the method according to the present invention including simultaneous stretching at a relatively lower temperature than the method of Patent Document 6, it is necessary to extrude all layers of a multilayer film with the same width, and to grip all the layers simultaneously with a clip during stretching. It is also clear that known techniques can be applied to the free end of the film, which is more economically advantageous in principle. It is also apparent that larger belt widths can be used if desired, with area stretch ratios exceeding 64 or even 46 or less. Further, the protective film can be manufactured as a shrink film having shrink characteristics suitable for a packaged product.

  The possibility of stretching in which the network structure in the ethylene-vinyl alcohol copolymer protective layer and the adjacent network structure are not formed due to the phase change that occurs when stretching at a temperature of 145 ° C. or less and the pressing of the crystallization process are carried out.

  As examples of each constituent layer, various appropriate configurations of layer A / layer B / layer C / layer D / layer C / layer B / layer E will be described in more detail below.

Protective inner layer D comprising ethylene-vinyl alcohol copolymer:
The inner layer D containing an ethylene-vinyl alcohol copolymer is at least 50% by weight, preferably 70-100% by weight, in particular 80-100% by weight of the ethylene-vinyl alcohol-copolymer (EVOH) described later, with respect to each layer D. including.

  The ethylene-vinyl alcohol copolymer is conventionally known and is produced by saponification or hydrolysis of an ethylene-vinyl acetate copolymer. For the purposes of the present invention, ethylene-vinyl alcohol copolymers having a degree of hydrolysis of 96-99% are particularly suitable. The melting point of an appropriate ethylene-vinyl alcohol copolymer is generally 150 ° C. or higher. In the present invention, the ethylene-vinyl alcohol copolymer has an ethylene concentration of 40 mol% or less, and the thickness of the ethylene-vinyl alcohol copolymer protective layer is usually 1 to 10 μm, preferably 1 It is in the range of ~ 6 μm, in particular 1 to 3 μm.

Adhesive layer C:
It is necessary to bond and bond the inner layer D, which is an ethylene-vinyl alcohol copolymer protective layer, and the structural layer B through the adhesive layer C. Therefore, an adhesion layer is provided between the inner layer D made of ethylene vinyl alcohol (EVOH) and the structural layer B made of partially crystalline polyolefin. The adhesion layer C firmly adheres the inner layer D and the structural layer B of the ethylene-vinyl alcohol copolymer to each other, and maintains adhesion between the inner layer D and the structural layer B on both sides of the adhesion layer C. Both the inner layer D and the structural layer B can be integrally stretched together with the adhesion layer C, and directivity can be imparted to a plurality of layers integrally and simultaneously with a simultaneous stretching device. The adhesion layer C is based on a modified polyolefin.

  The modified polyolefin is based on an ethylene polymer or a particularly suitable propylene polymer and is a propylene homopolymer, propylene copolymer or propylene trimer. The propylene copolymer or propylene trimer may contain at least 80 to 98% by weight of an overwhelming propylene unit and an appropriate amount of additional ethylene and / or butylene units as a comonomer. The polymer may be modified with maleic anhydride, optionally other carboxylic acid monomers or other esters such as acrylic acid or other derivatives.

  Modified polypropylene and modified polyolefin are known, for example, Miter Chemicals trade name Admer, Mitsubishi Chemicals trade name Modic, Chemplex trade name Plexar, Eastman trade name Epilene. It is sold under the trade name Bynel, manufactured by DuPont.

  For the purposes of the present invention, it is modified with maleic anhydride (for example, Mitsui Chemicals Q series product) and has a melt index of 230 ° C. (ASTM-D-1238) in the range of 1-10 g / 10 min. (Vicat) A propylene homopolymer or propylene copolymer having a softening point between 110 and 155 ° C. is preferred.

  The thickness of the adhesion layer C is generally from 0.3 to 5 μm, preferably from 0.3 to 3 μm, in particular from 0.3 to 2 μm.

Layer B:
Layer B is a structural layer made of polyolefin, particularly polypropylene, capable of imparting biaxiality, and generates sufficiently large adhesion strength to adhesion layer C while maintaining adhesion during simultaneous stretching at a temperature of 145 ° C. or lower. Should.

  A partially crystalline polyolefin having a crystallinity of layer C of at least 10 to 70%, preferably 30 to 70% and a melting point of at least 110 degrees is suitable.

  The polyolefin is based on a propylene polymer and is preferably a propylene homopolymer, a propylene copolymer or a propylene trimer. The propylene copolymer or propylene trimer preferably contains at least 80 to 98% by weight of an overwhelming propylene unit and an appropriate amount of additional ethylene and / or butylene units as a comonomer.

  The propylene polymers can be used individually or as a mixture. Modifications that allow stretching temperatures of 145 ° C. or lower may also be used. For example, atactic PP (polypropylene), syndiotactic PP, hydrocarbon resin, ethylene-propylene copolymer, propylene-butylene copolymer, ethylene-propylene-butylene-trimer, polybutylene, recycled PP and linear low density polyethylene It is preferable to use (PE-LLD) as a modified substance to a certain extent.

  It is preferable to use a propylene polymer having an ethylene concentration of 0 to 15% by weight based on the total polymer. In particular, isotactic propylene polymers having a melting point of 150-170 ° C. and a melt index (measured DIN 53735 at 21.6 N load and 230 ° C.) of 1.0-15 g / 10 min are suitable. The crystallinity of the propylene polymer is preferably 40 to 70%. The molecular weight distribution of the homopolymer can be varied. The ratio of the weight average Mw to the quantity average Mn is usually between 1 and 15.

  The layer thickness of layer B is preferably between 3 and 35 μm, in particular 3 to 15 μm.

  In another embodiment, layer B may be an opaque layer, such as an opaque base layer of a known opaque biaxial polypropylene film. In this embodiment, layer B becomes opaque due to the addition of filler. In this embodiment, layer B usually comprises at least 70% by weight of partially crystalline polyolefin, based on the weight of layer B. The filler concentration in the opaque layer B is preferably between 10 and 50% by weight with respect to the weight of the layer B. In the present invention, the filler is also a particle having a pigment and / or voids, and is a material known per se.

  Conventional pigments and / or particles having voids include, for example, aluminum oxide, aluminum sulfate, barium sulfate, calcium carbonate, magnesium carbonate, silicates such as aluminum silicate and magnesium silicate, and inorganic particles such as silicon dioxide and / or Organic particles. As the organic filler having voids, polymers that are not compatible with the polymer of the base layer conventionally used for this purpose, in particular, high density polyethylene (HDPE), cyclic such as norborn or tetracyclododecane having ethylene or propene. Olefin copolymers, polyesters, polystyrene, polyamides, and halogenated organic polymers are problematic, and polyesters such as polybutylene terephthalate are preferred.

Depending on the structure of the opaque layer B, the density of the opaque layer B and the film can be varied in the range of 0.4 to 1.1 g / cm ³ .

Cover layers A and E
The film according to the invention additionally has a structure comprising an ethylene-vinyl alcohol copolymer protective layer D, two adhesion layers C and a polyolefin layer B, as well as both surfaces of layer B by means of a cover layer of the same or different material. It is preferable to cover.

  This polyolefin cover layer constitutes a layer that is placed outside the finished multilayer film structure and has functions such as sealability, gloss, friction, etc., due to additional processing, printing, coating and metal plating possibilities. decide.

  Examples of olefin polymers suitable for the cover layer are polyethylene, polypropylene, polybutylene or mixed polymers with olefins having from 2 to 8 carbon atoms, copolymers of ethylene, propylene and / or butylene units, three Preference is given to monomers or mixtures of said polymers.

  The thickness of each cover layer is preferably larger than 0.1 μm and preferably in the range of 0.5 to 10 μm.

  The cover layer and / or layer B additionally contains known additives such as neutralizers, stabilizers, antistatic agents, ultraviolet and photoprotective agents, anti-clogging agents and / or lubricants in effective amounts. May be included.

  Embodiments in which corona, plasma or flame heat treatment is applied to the surface of the cover layers A and / or E are also included in the present invention. These treatments improve the adhesion to printing inks, adhesives, room temperature sealing layers, metal layers and the like by known methods.

  Depending on the intended end use, the total thickness of the film according to the invention can be varied within wider limits. The total thickness is preferably 4 to 100 μm, in particular 5 to 80 μm, more preferably 6 to 60 μm.

  In order that those skilled in the art will be able to practice the method conditions, materials and film properties of the present invention and to understand other objects and advantages, embodiments of the present invention are described in more detail below.

  Among the examples, Examples 1 to 17 are a multilayer film having a total of 7 layers having the ethylene-vinyl alcohol copolymer layer of the structural layer A / layer B / layer C / layer D / layer C / layer B / layer E. The manufacturing method of Example 1 is demonstrated, and Examples 1-6 are comparative examples.

In each example, the following types of materials were used as materials indicating the treatment names.
HP522H: Isotactic structural polypropylene homopolymer "Moplen (registered trademark)" HP522H manufactured by Basel
HP422H: Isotactic polypropylene homopolymer “Moplen (registered trademark)” manufactured by Basel, Inc. HP422H (Minirandom ethylene concentration about 1.5%)
"Admer (registered trademark)"-QF551E: Anhydrous polypropylene resin manufactured by Mitsui Chemicals
7372-XCP: Basel polypropylene trimer "Adsyl (registered trademark)" 7372-XCP
5C37-F: Basel Polypropylene Trimer “Adsyl (registered trademark)” 5C37F
MA-0935-PP: Constab Polypropylene Masterbatch containing 50% hydrocarbon (Masterbatch)
LC101-B: EVAL-EUROPE manufactured ethylene-vinyl alcohol-copolymer “EVAL (registered trademark)” LC101B containing an ethylene concentration of 27 mol%
F101-B: an ethylene-vinyl alcohol-copolymer “EVAL (registered trademark)” F101B containing an ethylene concentration of 32 mol% manufactured by EVAL-EUROPE
H101-B: An ethylene-vinyl alcohol-copolymer “EVAL (registered trademark)” H101B containing an ethylene concentration of 38 mol% manufactured by EVAL-EUROPE
ES104-B: EVAL-EUROPE's ethylene-vinyl alcohol-copolymer “EVAL (registered trademark)” containing an ethylene concentration of 44 mol% ES104B
G156-B: An ethylene-vinyl alcohol-copolymer “EVAL (registered trademark)” G156B containing an ethylene concentration of 48 mol% manufactured by EVAL-EUROPE
SP482-B: EVAL-EUROPE's ethylene-vinyl alcohol-copolymer “EVAL (registered trademark)” SP482B containing an ethylene concentration of 32 mol%

[Example]
[ Before Example 1 ]
In the example, a 7-layer protective multilayer film having an ethylene-vinyl alcohol copolymer layer as an inner layer was produced, and 7-layer extrusion was performed on a cooling roller with a wide slit melt nozzle. A seven-layer initial film formed by a cooling roller was immediately and simultaneously stretched by a Laboratoriums-LISIM (registered trademark) stretching device manufactured by (Brueckner).

At that time, the arrangement layer A / layer B / layer C / layer D / layer C / layer B / layer E of the melt for producing the multilayer film is formed from a given conveying device by the following nozzle device.
Layer A—outer layer, air knife side: 43 mm single screw extruder Extrusion layer B—intermediate layer: twin screw extruder with 55 mm melt pump Layer C—adhesion layer: 35 mm melt pump Single screw extruder with layer D-ethylene-vinyl alcohol copolymer core layer: single screw extruder with 35 mm melt pump Layer E-outer layer, cooling roller side: 50 mm single shaft Screw extruder

  It should be noted that layers A to E are labeled according to the placement or position of the wide slit nozzle of the melt extruder relative to the cooling roller and the opposing air knife.

  In Examples 1 to 6, which show comparative examples, an ethylene-vinyl alcohol copolymer layer is provided as an inner layer under conditions optimized for imparting simultaneous directionality of a biaxially oriented polypropylene film (s-BOPP film). Directionality is imparted to the protective multilayer film of the layer. The conditions to be optimized are biaxial polypropylene films with the desired combination of mechanical and optical properties for good thickness tolerances and the operational safety necessary to establish economical manufacturing. Supply. The stretching temperature using standard polypropylene homopolymer is in the range of 150-160 ° C, preferably 155 ° C.

  In Examples 7 to 17 according to the present invention, a seven-layer protective multilayer film having an ethylene-vinyl alcohol copolymer layer as an inner layer is stretched at a temperature of 145 ° C. or lower, particularly 140 ° C. or lower, preferably approximately 135 ° C. . In so doing, in order to lower the stretching temperature, a modification of layer B is required which can be achieved using layer B and using the materials shown in examples 7-17.

[ Example 1 ] (Comparative example)
The operating conditions of the material and the five extruders are as follows.
Layer A: Extruder with 5C37-F, extraction temperature 240 ° C Layer B: Extruder with HP-522H, extraction temperature 258 ° C Layer C: Extruder with Admer-QF551E, extraction temperature 236 ° C Layer D: G156- B, Extruder with extraction temperature of 186 ° C Layer E: 5C37-F, Extruder with extraction temperature of 240 ° C

The initial film obtained by co-extrusion of the 7-layer melt is printed before stretching on the base film under conditions optimized for the simultaneous orientation of biaxially oriented polypropylene film (S-BOPP film). Depending on the enlargement ratio of the lattice, directionality was imparted by stretching 7 times in the machine direction (MD) and stretching 6 times in the transverse direction (TD). The stretching temperature in the stretching section was 158 ° C. The relaxation rate was 5% in the longitudinal direction and 5% in the lateral direction. A film having a total thickness of 20 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (Layer D) was approximately 1.4 m. The appearance of the film obtained was brilliant and no network structure was observed. Tensile strength, longitudinal direction 241n / mm ^2, in the transverse direction was 187N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2471N / mm ^2, in the transverse direction was 1929N / mm ^2. The elongation at break was 93% in the longitudinal direction and 143% in the lateral direction. The turbidity value was 1.0%. The gloss was 91. The shrinkage rate at 120 ° C. for 5 minutes was 4.1% in the longitudinal direction and 3.1% in the lateral direction. However, the oxygen barrier was only 81.2 cm ³ / m ² dbar.

[ Example 2 ] (Comparative example)
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-ES104-B having an ethylene concentration of 44 mol% and 100 wt% was used for layer D. The extraction temperature was 223 ° C. The stretching temperature in the stretching section was 156.5 ° C. A film having a total thickness of 20 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.8 μm. The appearance of the resulting film was brilliant and no network structure was observed. Tensile strength, longitudinal direction 238N / mm ^2, in the transverse direction was 193N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2480N / mm ^2, in the transverse direction was 2090N / mm ^2. The elongation at break was 95% in the longitudinal direction and 134% in the lateral direction. The turbidity value was 0.95%. The gloss was 91. The shrinkage rate at 120 ° C. for 5 minutes was 4.3% in the longitudinal direction and 4.1% in the lateral direction. However, the oxygen barrier was only 62.7 cm ³ / m ² dbar.

[ Example 3 ] (Comparative example)
A film was prepared as in Example 1. Unlike Example 1, 100% by weight ethylene-vinyl alcohol-copolymer EVAL-H101-B with an ethylene concentration of 38 mol% was used for layer D. The extraction temperature was 208 ° C. The stretching temperature in the stretching section was 155.5 ° C. The draw ratio was 7 in the machine direction and 6.5 in the transverse direction. A film having a total thickness of 20 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (Layer D) was approximately 1.7 μm. The resulting film had a cloudy appearance and a strong network structure.

[ Example 4 ] (Comparative example)
A film was produced in the same manner as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-F101-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. The extraction temperature was 208 ° C. The stretching temperature in the stretching section was 158.5 ° C. The draw ratio was 7 in the machine direction and 6 in the transverse direction. A film having a total thickness of 20 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (Layer D) was approximately 1.7 μm. The resulting film had a cloudy appearance and a strong network structure.

[ Example 5 ] (Comparative example)
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-LC101-B having an ethylene concentration of 27 mol% and 100 wt% was used for layer D. The extraction temperature was 207 ° C. The stretching temperature in the stretching section was 156.5 ° C. The draw ratio was 7 in the machine direction and 6.7 in the transverse direction. A film having a total thickness of 18 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.1 μm. The appearance of the obtained film was cloudy and a strong network structure was observed.

[ Example 6 ] (Comparative example)
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-SP482-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. This new EVAL type should guarantee improved optical properties during corresponding protection. The extraction temperature was 207 ° C. The stretching temperature in the stretching section was 157.5 ° C. The draw ratio was 7 in the machine direction and 6.2 in the transverse direction. A film having a total thickness of 15.5 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.2 μm. The appearance of the obtained film was slightly turbid. There were small spots on the film, but no network structure was observed. However, the oxygen barrier was only 185 cm ³ / m ² dbar.

[ Example 7 ]
A film was prepared as in Example 1. Unlike Example 1, 100% by weight ethylene-vinyl alcohol-copolymer EVAL-H101-B with an ethylene concentration of 38 mol% was used for layer D. The extraction temperature was 226 ° C. A mixture of 50% by weight of polypropylene homopolymer (HP522-H) and 50% by weight of polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 137.5 degreeC. The draw ratio was 6 in the machine direction and 5.8 in the transverse direction. A film having a total thickness of 19 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.7 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 210N / mm ^2, in the transverse direction was 179N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 1830N / mm ^2, in the transverse direction was 1638N / mm ^2. The elongation at break was 84% in the longitudinal direction and 93% in the lateral direction. The turbidity value was 1.8%. The gloss was 89. The shrinkage ratio at 120 ° C. for 5 minutes was 13.2% in the longitudinal direction and 14.1% in the lateral direction. The oxygen barrier property was 6.2 cm ³ / m ² dbar.

[ Example 8 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-F101-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C.
A mixture of 50% by weight of polypropylene homopolymer (HP522-H) and 50% by weight of polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area could be reduced to 137 degreeC. The draw ratio was 6 in the machine direction and 6 in the transverse direction. A film having a total thickness of 19 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (Layer D) was approximately 1.4 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 181N / mm ^2, in the transverse direction was 204N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 1591N / mm ^2, in the transverse direction was 1739N / mm ^2. The elongation at break was 87% in the longitudinal direction and 77% in the lateral direction. The turbidity value was 2.0%. The gloss was 89. The shrinkage ratio at 120 ° C. for 5 minutes was 14.1% in the longitudinal direction and 15.5% in the lateral direction. The oxygen barrier property was 3.0 cm ³ / m ² dbar.

[ Example 9 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-F101-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C. A mixture of 60% by weight polypropylene homopolymer (HP522-H) and 40% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 138.5 degreeC. The draw ratio was 7 in the machine direction and 5.8 in the transverse direction. A film having a total thickness of 16.5 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.3 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 253N / mm ^2, in the transverse direction was 170N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2408N / mm ^2, in the transverse direction was 1772N / mm ^2. The elongation at break was 62% in the longitudinal direction and 98% in the transverse direction. The turbidity value was 2.1%. The gloss was 88. The shrinkage rate at 120 ° C. for 5 minutes was 14.0% in the longitudinal direction and 11.1% in the lateral direction. The oxygen barrier property was 3.0 cm ³ / m ² dbar.

[ Example 10 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-F101-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C. A mixture of 60% by weight polypropylene homopolymer (HP522-H) and 40% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 137.5 degreeC. The draw ratio was 6 in the machine direction and 5.8 in the transverse direction. A film having a total thickness of 20 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.6 μm. The relaxation rate was 15% in the longitudinal direction and 15% in the lateral direction. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 217N / mm ^2, in the transverse direction was 156N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 1929N / mm ^2, in the transverse direction was 1572N / mm ^2. The elongation at break was 82% in the longitudinal direction and 116% in the lateral direction. The turbidity value was 2.2%. The gloss was 85. The shrinkage rate at 120 ° C. for 5 minutes was 5.1% in the longitudinal direction and 4.8% in the lateral direction. The oxygen barrier property was 3.3 cm ³ / m ² dbar.

[ Example 11 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-F101-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C. A mixture of 80% by weight polypropylene homopolymer (HP522-H) and 20% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 135.0 degreeC. The draw ratio was 7 in the machine direction and 5.8 in the transverse direction. A film having a total thickness of 17 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.4 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 269N / mm ^2, in the transverse direction was 187N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2618N / mm ^2, in the transverse direction was 2063N / mm ^2. The elongation at break was 65% in the longitudinal direction and 87% in the transverse direction. The turbidity value was 2.2%. The gloss was 83. The shrinkage ratio at 120 ° C. for 5 minutes was 14.0% in the longitudinal direction and 10.2% in the lateral direction. The oxygen barrier property was 3.0 cm ³ / m ² dbar.

[ Example 12 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-LC101-B having an ethylene concentration of 27 mol% and 100 wt% was used for layer D. The extraction temperature was 217 ° C. A mixture of 80% by weight polypropylene homopolymer (HP522-H) and 20% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 136.0 degreeC. The draw ratio was 7 in the machine direction and 5.8 in the transverse direction. A film having a total thickness of 16.4 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.4 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 260 N / mm ^2, in the transverse direction was 189N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2547N / mm ^2, in the transverse direction was 2092N / mm ^2. The elongation at break was 64% in the longitudinal direction and 85% in the transverse direction. The turbidity value was 1.7%. The gloss was 88. The shrinkage ratio at 120 ° C. for 5 minutes was 11.6% in the longitudinal direction and 9.6% in the lateral direction. The oxygen barrier property was 2.3 cm ³ / m ² dbar.

[ Example 13 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-LC101-B having an ethylene concentration of 27 mol% and 100 wt% was used for layer D. The extraction temperature was 217 ° C. A mixture of 80% by weight polypropylene homopolymer (HP522-H) and 20% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 136.0 degreeC. The draw ratio was 6.3 in the machine direction and 5.2 in the transverse direction. The relaxation rate was 15% in the longitudinal direction and 15% in the lateral direction. A film having a total thickness of 21.0 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.7 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 225N / mm ^2, in the transverse direction was 159N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2133N / mm ^2, in the transverse direction was 1868N / mm ^2. The elongation at break was 85% in the longitudinal direction and 97% in the lateral direction. The turbidity value was 1.6%. The gloss was 89. The shrinkage rate at 120 ° C. for 5 minutes was 3.0% in the longitudinal direction and 3.1% in the lateral direction. The oxygen barrier property was 2.0 cm ³ / m ² dbar.

[ Example 14 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-F101-B having an ethylene concentration of 32 mol% and 100 wt% was used for layer D. The extraction temperature was 217 ° C. A mixture of 80% by weight polypropylene homopolymer (HP522-H) and 20% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 136.5 degreeC. The draw ratio was 6 in the machine direction and 5.3 in the transverse direction. The relaxation rate was 15% in the longitudinal direction and 15% in the lateral direction. A film having a total thickness of 20.0 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.7 μm. The resulting film had a lustrous appearance and did not have any network structure. Tensile strength, longitudinal direction 231N / mm ^2, in the transverse direction was 168N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2118N / mm ^2, in the transverse direction was 1807N / mm ^2. The elongation at break was 88% in the longitudinal direction and 107% in the lateral direction. The turbidity value was 1.5%. The gloss was 89. The shrinkage rate at 120 ° C. for 5 minutes was 3.3% in the longitudinal direction and 1.9% in the lateral direction. The oxygen barrier property was 2.8 cm ³ / m ² dbar.

[ Example 15 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-H101-B having an ethylene concentration of 38 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C. A mixture of 80% by weight polypropylene homopolymer (HP522-H) and 20% by weight polypropylene trimer (7372-XCP) was used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 136.0 degreeC. The draw ratio was 7 in the machine direction and 6 in the transverse direction. A film having a total thickness of 16.0 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.3 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 264N / mm ^2, in the transverse direction was 200 N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2526N / mm ^2, in the transverse direction was 1998N / mm ^2. The elongation at break was 73% in the longitudinal direction and 99% in the transverse direction. The turbidity value was 1.4%. The gloss was 90. The shrinkage ratio at 120 ° C. for 5 minutes was 9.9% in the longitudinal direction and 8% in the lateral direction. The oxygen barrier property was 8.2 cm ³ / m ² dbar.

[ Example 16 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-LC101-B having an ethylene concentration of 27 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C. 100% by weight of polypropylene minirandom (HP422-H) with an ethylene concentration of 1.5% was used for layer B. Thereby, the extending | stretching temperature in an extending | stretching area was able to be reduced to 135 degreeC. The draw ratio was 6 in the machine direction and 6 in the transverse direction. A film having a total thickness of 17.0 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.5 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 224N / mm ^2, in the transverse direction was 210N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2376N / mm ^2, in the transverse direction was 2376N / mm ^2. The elongation at break was 76% in the longitudinal direction and 75% in the lateral direction. The turbidity value was 0.95%. The gloss was 91. The shrinkage ratio at 120 ° C. for 5 minutes was 7.6% in the longitudinal direction and 7.4% in the lateral direction. The oxygen barrier property was 1.8 cm ³ / m ² dbar.

[ Example 17 ]
A film was prepared as in Example 1. Unlike Example 1, an ethylene-vinyl alcohol-copolymer EVAL-LC101-B having an ethylene concentration of 27 mol% and 100 wt% was used for layer D. The extraction temperature was 218 ° C. A mixture of 90% polypropylene minirandom (HP422-H) with 1.5% ethylene concentration and 10% polypropylene masterbatch (MA-0935-PP) with 50% hydrocarbons. Used for layer B. Thereby, the extending | stretching temperature of the extending | stretching area was able to be reduced to 135.0 degreeC. The draw ratio was 6 in the machine direction and 6.2 in the transverse direction. A film having a total thickness of 17.5 μm was obtained, and the thickness of the ethylene-vinyl alcohol copolymer layer (layer D) was approximately 1.5 μm. The appearance of the resulting film was brilliant and did not have any network structure. Tensile strength, longitudinal direction 231N / mm ^2, in the transverse direction was 195 N / mm ^2. Young thermal expansion material coefficient (E module) in the longitudinal direction 2807N / mm ^2, in the transverse direction was 2626N / mm ^2. The elongation at break was 77% in the longitudinal direction and 77% in the transverse direction. The turbidity value was 0.93%. The gloss was 92. The shrinkage was 7.2% in the longitudinal direction and 6.8% in the lateral direction at 120 ° C. for 5 minutes. The oxygen barrier property was 1.7 cm ³ / m ² dbar.

[ Result ]
The results of the film production test described in the above examples show that, according to the present invention, a biaxial polypropylene film having an ethylene-vinyl alcohol copolymer protective layer with outstanding protective properties and more prominent and desirable combination properties for packaging purposes. In addition to the points obtained, outstanding properties relating to fragrance and odor sealing and other outstanding protective properties, it is demonstrated that very good film strength, rigidity and outstanding optical properties are obtained. It is also possible to combine the protective property with the shrinkage property.

  The range of production conditions shown in the above examples is limited by the equipment that can be used during the experiment, but the given specific process conditions do not represent the limits of the present invention or the film production process according to the present invention. Depending on the intended use of the film, protective layer thicknesses of up to 10 μm can be obtained, for example, if necessary.

  In addition, since the film obtained can be stabilized by controlling the conditions of simultaneous stretching, the shrinkage rate is 5% or less in one or both of the main directions corresponding to the machine direction (MD) or the transverse direction (TD) during production. It can be pointed out that can be obtained. However, it is possible to select a stretching condition that makes the unidirectional or bidirectional shrinkage at 120 ° C. 15% or more.

  Furthermore, it can be pointed out that in the seven-layer structure, one polypropylene layer B can be produced according to the end use to be used, even if a recycled polypropylene product or a polyolefin different from the polypropylene used for the other layer B is used. .

  Based on outstanding protective properties, the film of the present invention is suitable for all packaging purposes in which the packaged goods are not subject to fragrance loss and / or odor diffusion does not occur through the packaging. The slight oxygen permeability and the slight vapor permeability of the film according to the invention are suitable for the most frequent use of biaxial polypropylene films coated with polyvinyl alcohol (PVOH) or polyvinylidene chloride (PVDC), which are more expensive than the present .

  A particularly preferred method of use is for the packaging of foodstuffs such as fresh foodstuffs, confectionery and cakes. For example, films can be used for packaging other products such as medicines. Based on good optical properties, the film can be used in all cases where consumers expect a transparent protective material.

Claims (21)

Protective film for packaging in the form of a multilayer film based on a biaxially oriented polyolefin film with at least one functional or protective layer coextruded based on ethylene-vinyl alcohol copolymer (EVOH) In
Produced by co-extrusion of a co-extruded multilayer initial film, having an ethylene-vinyl alcohol copolymer layer with a thickness of at least 5 μm, an oxygen transmission rate (OTR; ASTM at a temperature of 23 ° C. and a relative humidity of 75% -3985) is less than 10 cm ³ / m ² dbar,
Layer B / Layer C / Layer D / Layer C / Layer B have at least a five-layer structure, and both layers B constitute a structural layer based on biaxial polyolefin, Each comprises an adhesive layer based on a modified polyolefin, and layer D comprises a protective layer based on an ethylene-vinyl alcohol copolymer having an ethylene molar concentration of 40 mol% or less,
The protective film characterized in that the polyolefin of at least one layer B constitutes a partially crystalline thermoplastic polypropylene and / or modified polypropylene imparted with biaxiality by simultaneous stretching at a temperature of 145 ° C. or lower.   7 layer structure of layer A / layer B / layer C / layer D / layer C / layer B / layer E, the same or different additional layer A and layer E can have desired sealability, adhesion improvement The protective film according to claim 1, which is a functional cover layer made of a modified polyolefin that achieves a desired friction value or gloss value and / or ensures printing, coating or metal plating.   The protective film according to claim 1 or 2, wherein the modified polyolefin of the adhesive layer C is a polypropylene or polyethylene modified with maleic anhydride.   Each adhesive layer C is a protective film of any one of Claims 1-3 which has the range of thickness 0.1-5 micrometers.   The partially crystalline thermoplastic polypropylene of layer B has at least 80 to 98% by weight of propylene units and the corresponding remaining ethylene units and / or butylene units, and is an isotactic propylene homopolymer, propylene copolymer The protective film according to claim 1, which is a modified polypropylene based on a coalescence or propylene trimer.   Layer B polypropylene is atactic polypropylene, syndiotactic polypropylene, hydrocarbon resin, ethylene-propylene copolymer, propylene-butylene copolymer, ethylene-propylene-butylene-trimer, polybutylene, recycled polypropylene and linear low The protective film of Claim 1 or 5 containing the modified material selected from a density polyethylene (PE-LLD) and its mixture.   The protective film according to claim 1, wherein at least one of the layers B additionally contains a filler and / or a pigment having voids, and is colored or opaque.   The thickness of each layer B exists in the range of 3-35 micrometers, The protective film in any one of Claims 1-7.   The tensile strength and elastic modulus in the machine direction (MD) of the film are equal to or higher than the tensile strength and elastic modulus in the transverse direction of the film, and the elongation at break in the transverse direction (TD) is the elongation at break in the machine direction. The protective film according to claim 1, which is the same as or higher than the protective film. Longitudinal and total Young thermal expansion material coefficient of lateral (E module) The protective film according to any one of claims 1 to 9, greater than 2000N / mm ^2.   The protective film according to claim 1, which has a gloss of 80 or more (Gloss; ASTM-2457).   The protective film according to any one of claims 1 to 11, wherein the film is free of fillers and pigments and has a turbidity of 5% or less (turbidity: ASTM-1003).   The protective film according to any one of claims 1 to 12, which is a shrink film having a shrinkage ratio of at least 10% in one or both main film directions within 5 minutes at a temperature of 12 ° C.   The thickness of a film exists in the range of 4-100 micrometers, The protective film in any one of Claims 1-13.   The protective film according to claim 1, wherein at least one surface of the film is subjected to metal plating. In the manufacturing method of the protective film for packaging of any one of Claims 1-15,
50% / second by coextruding the polymer constituting the initial multilayer film layer on the cooling roller from the required number of wide slit nozzles as a melt, and at a stretching temperature of 145 ° C. or less and at least 10 times the area expansion Applying the above stretching speed and performing simultaneous stretching without contact with the initial multilayer film to be formed by a simultaneous stretching apparatus.   The manufacturing method according to claim 16, wherein the initial multilayer film is stretched at least three times the initial measured value in the longitudinal direction and the transverse direction.   The manufacturing method of Claim 16 or 17 which implements simultaneous extending | stretching by the simultaneous extending | stretching apparatus (LISIM (trademark)) provided with a linear motor drive device, and extends | stretches a planar film.   The protective film manufactured by the method of any one of Claims 16-18.   A method for using a protective film, wherein the protective film according to any one of claims 1 to 15 and 19 is used as a packaging film for fragrance, odor and oxygen-sealing food products and luxury products.   The use method of the protective film characterized by using the protective film of any one of Claims 1-15 and 19 as a cover film.